Telephone circuits



June 2, 1925 1,540,421

w. T. POWELL TELEPHONE CIRCUITS I Filed June 5 19.24

INV ENTO R Winf red T Poweil ATTORNEY Patented June 2, 1925.

UMTFED STATES E OFFieE;

WINIFRED '1. IEGWELL, OF ROCHESTE'E, NEW YORK, iiSSIGNO RVTO THE SEROMBERG- CARLSON 'TELEPHONE MANUFACTURE l CORPORATION or new YORK.

Application filed June 5,

To all whowrz't may 00mm; 1

.Be it known that I, "Vrnrnnn T. POWELL, a citizen of'the United Stetes,residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Telephone Circuits,of Whichthe following is e full, clear, concise, and exact description This invention relates to telephone circuits and more particularly to the circuits of e telephone set including a receiver and a telephone.transmitter.

It is an object of the present invention to provide circuit arrangements which will deliver the maximum amount of energydn the forin of an outgoing signal to telephone line and Which will receive the maximum amount of energy in the form of an incoming signal "from said telephone line Without "the disturbance of the receiving circuit by the transinission circuit, which disturbance is commonly known as 9 sidetone in thereeeiver. In other Words'it is .the object of the invention to provides. circuit arrangement for preventing ta llring currents in the talking net-Work from interiering seriously 'W'ith the receiving network.

In the embodiment of the invention herein disclosed well-kriowir substation equipment such as a receiver, fixed condenser and a signal or ringer, are associated in a circuit net-Work with e two-element "tra1ismitter and an induction coil having leads from its mid-point, to wl'iich certein elements of the transmitter are connected. w

In the drawings Fig. 1 diugi'uinmatically represents the invention applied to the substation circuits of a manual telephone'line. Fi 2 shows arsi nilar substation circuit or rangen'ient in which a ivell -knotvn impulse transmitter ithu shunt spring combination are provided for use when the substation circuit is incorporetec'l inanziutoinetic' telephonesystern.

The transmitter herein referred to as a two-element transmitter, may consist of udiziphrngin, on each side of which carbon button impinges. ,Other types of trainsmitters-such as electromagnetic or electrostatic transmitters may be employed.

The impulse transmitterherein referred TGGOMPANY, or ROCHESTER, NEW norm, is

rELnrHoNE CIRCUITS] 1924. Serial no. 718,141.,

to, inziy be similar in construction toilet disclosed on pages 345 and of, Automatic Telephony, by Smith and Campbell, first edition, but in which a different shunt spring combination is provided,

Referring to Fig. 1, 5 designates the Well known receiver associated with a tWo-ele ment transmitter, which consistslof thefdia phragin 6 mounted to engaged by the carbon buttons 7 and 8. AniiiduetioncOil generally indicated as. 9,. includes the primary windings referred to as 10 and 11 and the secondary winding 12. The primary windings 10 and 11 are inductively related to the secondary Winding 12. The line conductors 13 and'14 are normally bridged by e circuit including the ringer 15 andthe fixed con-denser16, 17 indicates-e contact Whichis closed by the switchhoo'k 18 When the receiver 5 is removed there from. V I w j 7 hen the net-Work is usedto transmit outgoing currents, such currents do" not produce serious side-tone noises in the rethe first mentioned buttonlivi'll "be decreasing, While the resistance of the last men'- tioned button is increasing. This causes an increased'fl'oiv of cu'rrentthrough the winding 10 end a decreasedgflow of current through vindin'g 11.. The veluesof'the primary winding-s10 andll are such that the induced vol telgencross the secondary winding- 12, due to the current rise in the pri mary Winding 10,, is equal to the voltage across the mentioned secondary wii'iding 12, due to therdecreasedcurrent flow injiviiiding' 11. 'lhere't'ore, no current will flow in the receiver circuit end there will be no side-tone. It hi thisinstzrnt the Celfhonhut ten 8 is being. coinpressednnd the es lien button 7 expanded, the same i'esult'v'vill be accomplished because the current will rise in thewinding 11 when it {is decreasing in windinglQ'; I V g f The i present .circui'tf arrangement is designed ,to give an amplifiedsignuLwhich isleonimonly referred [to its the boosterfi described.

Assume that the current is decreasing through primary winding 10 due to the expansion of carbon button 7. At this time the current through primary winding 11 will be increasing, due to the compression of carbon button 8. This increase of current flow through winding 11 is et fective to induce a current flow in primary winding 10, which is in opposition to the line current normally included in con- (luctors 13 and 14, when the hookswitch contacts '17 and 18 are closed. The opposition of the induced current flow in the net-work to the line current results in the further reduction in the line current below the values, which would be due to the expansion of button 7.

lVhen the current through winding 1O is increasing and that through the winding 11 is decreasing, due to the alternate condition of the transmitter buttons 7 and 8, a decrease of current flow through winding 11 will induce a flow of current in winding 10, which is in the same direction as the line current, with the result that the current flow in the line conductors 13 and 1-1 will be increased over that caused'by the compression of carbon button 7.

When this net-work is employed in receiving signals, the incomingcurrents pass through the primary windings l0 and 11 of the. induction coil and transmitter button 8 in series. Part of the current after pass ing through the primary winding 10 flows through the transmitter button 7. These currents are always in the same direction in Cir both windings and are effective to produce an induced current in the closed circuit including the receiver 5.

In the modification shown in Fig. 2 the same reference characters are used to designate corresponding parts of Fig. 1. The network of Fig. 2 differs from that of Fig.

'1 by theinclusion of the impulse springs 19 of the well-known dial impulse sender.

and by the addition of the shunt springs 20 and conductor 21. The operation of this modification is identical with that of Fig. 1, except that during the period of sending impulses, that is, when the impulse springs 19 are intermittently closed by dial mechanism (not shown), the shunt springs 20 are closed and conductor 21 thereby causes a shunt about the receiver 5, to eliminate dial noises therefrom.

This shunt also extends about the transmitter so that the impedance thereof is not included in the impulse circuit.

\Vhat I claim is: a

1. In a telephone net-work, two line c011- ductors, a signal normally bridged across said line conductors, an induction coil having a secondary winding and a primary Wl11Cll11g, sald primary winding being sepa- *rated into two portions, a transmitter connected between said portions of the primary winding and in series therewith, a second bridge across said line conductors including said transmitter and the portions of said primary winding, and a closed circuit including a receiver and said secondary winding, said closed circuit being" conductively separated from said line conductors.

2. In a telephone net-work, two line con- "ductors, a signal normally bridged across said line conductors, an induction coil having a secondary winding and a primary winding, said primary winding being electrically divided into two portions, a transmitter having a diaphragm and a variable resistance unit at each, side of said diaphragm, two of the ends of said primary winding being connected to said line conductors, said transmitter diaphragm being connected to a third end of said primary winding, the fourth end of said primary winding being connected to one ofesaid variable resistance units, a conductor connected at one end to the other variable resistance unit and to one of said first mentioned ends of said primary winding, and a circuit including said secondary winding and a receiver electrically related to said primary winding.

portions of the primary winding at the point of division, said primary winding being arranged for connection across said line conductors, a shunt circuit about one portion of said primary winding and terminat ing at one end in said telephone transmitter, and a receiver electrically connected to the ends of said secondary winding.

5. In a telephone net-work, two line conductors, a bridge across said line conductors includmg a condenser and arringer, an 1nduction coil having a secondary windingand a primary winding, said primary winding belng composed of two portions, a transmitter connected between the two portions ofsaid primary winding and in series therewith, a shunt circuit about one portion of said primary winding controlled by said transmitter, a secondbridge across said line conductors including both portions of said primary winding and said transmitter, and a receiver connected to the ends of said secondary winding;

6. In a telephone net-work, two line conductors, a bridge across said line conductors including a condenser and a ringer, an induction coil having a secondary winding and a primary winding, said primary Winding being composed of two portions, a transmitter connected between the two portions of said primary winding and in series therewith, a shunt circuit about one portion of said primary winding controlled by said transmitter, a second bridge across said line conductors including both portions of said primary Winding and said transmitter, and a closed circuit including a receiver connected to said secondary winding, said closed circuit being conductively separated from but inductively connected to said primary Windin 7. In a telephone net-work, a pair of line conductors, a bridge circuit across said line conductors, a two-element transmitter hav-' ing its elements connected in multiple in said bridge clrcuit, a telephone receiver, and

a circuit therefor inductively connected to but conductivelyseparated from said line conductors.

8. In a telephone net-work, a pair of line conductors, a bridge circuit across said conductors, a transmitter comprising a diaphragm and a button engaging each side of said diaphragm, the buttons of said transmitter being connected in multiple in said bridge circuit, a telephone receiver, and a closed circuit therefor inductively con nected to but conductively separated from said line conductors.

9. In a telephone netork, a pair of line conductors, a normally open bridge'including a two-element transmitter connected across saidline conductors, a second bridge including arringer and a condenser connected across said line conductors, a hookswitch for opening said first mentioned bridge, a telephone receiver, and a closed circuit for said receiver conductively separated from but inductively connected to said first bridge. In witness whereof, I hereunto subscribe my name this 4th day of June A. D. 19%.

IVINFRED T. POWELL. 

